November 14, 2016
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Higher vitamin D levels may reduce risk for breast cancer mortality

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Higher levels of vitamin D appeared associated with lower risk for breast cancer morbidity and mortality, especially among premenopausal women, according to a prospective cohort study published in JAMA Oncology.

Conversely, women with lower than 25-hydroxyvitamin D (25OHD) had a higher risk for advanced-stage tumors and triple-negative cancer.

Song Yao

“We found women with higher vitamin D levels in their blood following a breast cancer diagnosis had significantly better long-term outcomes,” Song Yao, PhD, associated professor of oncology at the department of cancer prevention and control at Roswell Park Cancer Institute, told HemOnc Today. “This adds to the growing body of evidence that vitamin D is an important nutrient and may play an important role in breast cancer.”

Vitamin D deficiency has been linked to a variety of cancers; however, many epidemiological studies and meta-analyses on the association between 25OHD levels and breast cancer have had mixed results.

In their study, Yao and colleagues evaluated how serum 25OHD levels collected within 2 months of breast cancer diagnosis correlated with prognostic characteristics and outcomes, including recurrence, second primary cancers and death.

Researchers collected data from 1,666 women (mean age, 58.7 years; standard deviation, 12.4) participating in the Pathways Study at Kaiser Permanente Northern California from Jan. 5, 2014, through March 15, 2015. Women completed emailed or telephoned questionnaires on lifestyle factors at baseline and 6, 24 and 72 months, and on health outcomes and comorbidities at 12, 24, 48, 72 and 96 months.

At baseline, 48% of the patient population was vitamin D deficient, and 35% was vitamin D insufficient. Blacks and Hispanics had lower 25OHD concentrations than whites, current smokers had lower concentrations than former or nonsmokers, and older women had higher concentrations than younger women.

Researchers reported mean serum 25OHD concentrations were lower in women with advanced-staged tumors, and the lowest in premenopausal women with triple-negative cancer (luminal A, 20 ng/mL; luminal B, 19.8 ng/mL; HER-2 enriched, 19.3 ng/mL; triple negative, 18.7 ng/mL).

Women with the highest concentration of 25OHD had superior OS (HR = 0.72; 95% CI, 0.54-0.98).

Among premenopausal women, the association between high levels of 25OHD and OS was even stronger (HR = 0.45; 95% CI, 0.21-0.96). For these women, higher levels of 25OhD also were associated with improved breast cancer–specific survival (HR = 0.37; 95% CI, 0.15-0.93) and invasive disease–free survival (HR = 0.58; 95%, 0.34-1.01), which includes recurrence and secondary primary invasive cancers, as well as death.

Premenopausal women with the lowest 25OHD concentrations had increased risk for triple-negative cancer compared with those within the highest two-thirds (tier 2 vs. tier 1, OR = 0.53; 95% CI, 0.27-1.04; tier 3 vs. tier 1, OR = 0.45; 95% CI, 0.25-0.83).

25OHD levels did not appear associated with risk for second primary cancers.

“Our findings are consistent with a bulk of previous literature showing high vitamin D levels linked with better breast cancer outcomes,” Yao said. “However, we did find the associations more prominent in women diagnosed with breast cancer before menopause.”

Yao and colleagues wrote that proving the causal relationship between 25OHD levels and cancer survival may be challenging because a feasibility study showed 84.4% of patients with newly diagnosed breast cancer reported use of vitamin-containing supplements, and only 12.7% of patients met the eligibility criteria, possibly due to increasing public and medical recognition of the benefits of vitamin D.

“Our study provides strong evidence that vitamin D may have independent effects on breast cancer survival,” Yao said. “As the next step, it will be critical to evaluate the benefits of vitamin D supplementation in improving breast cancer outcomes in a randomized clinical trial, which, however, may take years to come.” – by Chuck Gormley

For more information:

Song Yao, PhD, can be reached at song.yao@roswellpark.org.

Disclosure: The researchers report no relevant financial disclosures.